This policy setting allows you to manage whether Internet Explorer will launch COM add-ons known as browser helper objects such as toolbars. Browser helper objects may contain flaws such as buffer overruns which impact Internet Explorer's performance or stability.If you enable this policy setting Internet Explorer automatically launches any browser helper objects that are installed on the user's computer.If you disable this policy setting browser helper objects do not launch.If you do not configure this policy Internet Explorer automatically launches any browser helper objects that are installed on the user's computer.
Windows Components\Internet Explorer\Internet Control Panel\Advanced Page
At least Internet Explorer 6.0 in Windows 2003 Service Pack 1
HKCU\Software\Policies\Microsoft\Internet Explorer\Main!Enable Browser Extensions